The invention relates to a display device provided with a substantially evacuated envelope having mainly flat substantially parallel front and rear walls, a layer of luminescent material along the inner surface of the front wall and means for generating a plurality of electron beams which move substantially in a plane parallel to the front and rear walls and can be selectively deflected via deflection means in the direction of the layer of luminescent materials so that each beam scans at least a part of the layer of luminescent material.
A display device of this type has great advantages because thin, flat television screens can be realized therewith. For these devices research is being done to find such constructions that the use of thick glass walls, which is often necessary in connection with the high vacuum, can be avoided as much as possible. Other points of consideration are a uniform brightness throughtout the picture surface independent of the pixel driven and the possibility of integration with control electronics.
A display device of the type described in the opening paragraph is known from Netherlands Patent Application No. 7610521 laid open to public inspection, and corresponding to U.S. Pat. No. 4,028,582.
In this device electron beams are guided through channels and are subsequently not only deflected towards the phosphor screen, but the beams also perform a scanning movement in the transversal direction of the channel. This movement is carried out to simplify the electron gun for such a device.
The description of the electron gun in the patent application is limited. It is stated that only either one single source for one beam or a line cathode are arranged on and alongside the end walls of the channels, respectively.
The dimensions of conventional cathodes are such that electron beams generated from two cathodes located at a minimum distance from each other include a plurality of columns of pixels so that a horizontal deflection across a plurality of pixels is required in this case. Moreover the energy supplied is so high that such a solution is extremely costly for reasons of energy considerations and extra material costs (horizontal deflection electrodes in the channels).